The present invention relates to an integrated circuit device with improved electrostatic discharge protection (electrostatic discharge resistance), and an electronic instrument.
Along with an increase in the degree of integration and scaling down of integrated circuit devices (ICs), measures to prevent electrostatic discharge destruction (breakdown) have become increasingly important. Therefore, the IC manufacturer is required to produce highly reliable products which can pass a severe electrostatic discharge destruction test (e.g., JP-A-2000-206177).
JP-A-2006-100606 discloses an electrostatic protection circuit provided between circuits which differ in power supply system, for example.
The inventors of the invention discovered the following. For example, an interface circuit formed using a low-voltage transistor that operates utilizing a 1.8 V power supply is provided between a first circuit block formed using a low-voltage transistor that operates utilizing a 1.8 V power supply and a second circuit block formed using a low-voltage transistor that operates utilizing a 1.8 V power supply in another system. In this case, when static electricity of different polarities is applied between a power supply node of the first circuit block and a power supply node of the second circuit block, a gate insulating film of an insulated gate transistor which forms the interface circuit may break through a special electrostatic discharge destruction mechanism.
In one example of the new electrostatic discharge destruction mechanism discovered by the inventors, a first circuit block operates using a first high-potential power supply and a first low-potential power supply, a second circuit block operates using a second high-potential power supply and a second low-potential power supply, and the first circuit block and the second circuit block transmit signals through a buffer circuit that includes a pair of input/output buffers which operate using different power supply systems (i.e., first and second power systems). In this case, at least one of a first buffer circuit which contributes to signal transmission from the first circuit block to the second circuit block and a second buffer circuit which contributes to signal transmission from the second circuit block to the first circuit block is provided. For example, a positive electrostatic surge current is applied to the first high-potential power supply, and a negative electrostatic surge current is applied to the second low-potential power supply. Note that a positive electrostatic surge current may be applied to the second high-potential power supply, and a negative electrostatic surge current may be applied to the first low-potential power supply.
According to one example of the new electrostatic discharge destruction mechanism, the electrostatic surge energy partially flows through the buffer circuit which includes the pair of input/output buffers (i.e., flows through a normal signal transmission route), whereby the gate insulating film of the transistor which forms the input buffer tends to break. This electrostatic discharge destruction mechanism also relates to an electrostatic discharge protection circuit inserted between the low-potential power supplies, inter-power-supply protection circuits respectively provided for different power supply systems, and the like.
It is necessary to provide an additional element when providing an electrostatic discharge protection circuit aimed at electrostatic discharge protection. This increases the degree of complexity and the area of the circuit.
It is necessary to optimize an electrostatic discharge protection circuit in order to efficiently prevent electrostatic discharge destruction. In this case, optimization of the electrostatic discharge protection may become difficult due to limitations relating to the layout or the production process, for example.
In particular, it is important to reasonably dispose an electrostatic discharge protection circuit optimized while suppressing an increase in area at an effective position of a minute integrated circuit device (IC). It is difficult to deal with such a demand using related-art technology.